msm: mdss: fix cursor pipe idle checking mechanism

The clk status register and vbif status based on xin-id
is used to check if pipes are idle. VBIF checks cannot be done
for cursor pipes as the same xin-id is shared between dsi, cursor0
and cursor1. Avoid vbif status check and fix clk status check for
cursor pipes.

Change-Id: I9e0a185beffd4e732c1b5dc61822cc94b3735a27
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>